# medianにすればいいか
# WA出た
# median総数に足りない場合はmedianを下げる必要があるな

B = int(input())
N = int(input())
C = []
for i in range(N):
    C.append(int(input()))
C.sort()
sumC = sum(C)

from math import floor, ceil
if N%2 == 1:
    median = C[N//2]
    median = min(median, floor((sumC+B)/N))
    ans = 0
    for i in range(N):
        ans += abs(C[i]-median)
    #print(median, ans)
else:
    median_low = floor((C[N//2-1]+C[N//2])/2)
    median_low = min(median_low, floor((sumC+B)/N)) 
    ans_low = 0
    for i in range(N):
        ans_low += abs(C[i]-median_low)
    #print(median_low, ans_low)
    median_high = ceil((C[N//2-1]+C[N//2])/2)
    median_high = min(median_high, floor((sumC+B)/N)) 
    ans_high = 0
    for i in range(N):
        ans_high += abs(C[i]-median_high)
    #print(median_high, ans_high)
    ans = min(ans_low, ans_high)
print(ans)